Is ttl basically the same thing as auto except that ttl tells the flash what yur camera settings are and in auto u have to manually dial in the settings? Also, there is something called i-tt(for nikon) and a a comparable function for other camera manufacturers where teh camera shoots a quick preflash to determine exposure. What is, if any, the advantage to i-tt. Is it any more accurate than auto or ttl?
iTTL for Nikon is the auto mode. In iTTL mode, lens information is passed to the flash in order to compensate for distance, aperture, shutter speed, and focal length. On Canon, it is call eTTL and performs the same function as iTTL for Nikon. In Auto mode, the flash (strobe) just measures the reflectivity of the subject and computes an educated guess as to distance, etc. Using iTTL or eTTL mode will normally provide better results, less glare, and if done right less red-eye.
As with anything else, the anwer is: it depends. In a TTL flash system, the camera measures the flash through the lens (which is what TTL means) and tells the flash when to shut off. An auto flash measures the light itself. Both can be fooled by the same things, like a reflective surface or a large amount of dark colors in a shot. I use both kinds, and for me, the auto flash is more consistent. Yes, you have to set the ISO and aperture on the flash to match what you are using on the camera, where a TTL unit already knows these things. The camera and flash are not re-measuring the scene for each shot, which a TTL system does, and can give you widely variable results from shot to shot. The camera meter controls the flash, and if you meter on a bright spot one shot, and a dark spot the second shot, the flash output will be very different. An auto unit is measuring the entire scene each shot, not one specific area. What the TTL units make easy is fill flash. You don't have to measure or calculate or make a best guess as to the flash power, you just shoot and it works. Nikon even has a specific flash mode for this. I shoot E-TTL with Canon gear, although I find that it tends to underexpose the flash by 2/3 to 1 full stop, and that is with 2 different flashes. With my Sony digital, and Minolta and Nikon film cameras, I use all auto flashes. I get results as good, or better, than the E-TTL stuff, without the constant underexposure of the Canon system.
no it wont affect the warranty on it none ,but id be real careful ,some of those products don't really work to well and they just take your money.there a few that work though,stp makes a good product,and any advance auto parts has it in stock,the oil additives are a waste of money though,just use a good oil in it,good luck with it hope this helps.
